The invention relates to multidimensional vector quantization type speech coding devices used in, for example, automatic speech recognizers.
In vector quantization type speech coding devices, a number of different features of an utterance are measured during each of a series of successive time intervals to produce a series of feature vector signals represeting the feature values of the utterance. A plurality of multidimensional prototype vector signals are stored, where each dimension of a prototype vector signal has a parameter value representing one of the features being measured. The identity of the prototype vector signal having parameter values which are closest to a given feature vector signal is output as a "label" of that feature vector signal.
As the number of prototype vector signals increases, and as the number of different features (dimensions) increases, the vector quantization process (and therefore speech recognition) becomes more costly and more time-consuming. Moreover, the storage of vector quantization prototype vector signals occupies increasing electronic memory.